Assessment of Inter- and Intra-Rater Reliability of Tablet-Based Software to Measure Cochlear Duct Length

Investigation of Automated Cochlear Length and Cochlear Implant Insertion Angle Predictions with a Surgical Planning Platform

INTRODUCTION

Preoperative anatomical assessment is essential to optimize the outcome of individualized cochlear implantation. Algorithms based on cochlear diameters simplify this evaluation. The new version of a surgical planning platform is capable of performing this determination automatically. Our study evaluated the robustness of automated measurements and compared individual differences between automated and manual measurements, including predicting cochlear duct length and insertion angles.

MATERIALS AND METHODS

The preoperative cone beam CT scans of 55 MED-EL cochlear implant patients were analyzed. Using the surgical planning platform, the anatomical diameters were measured automatically and manually. The values were compared, as well as the predictions of the insertion angles and prediction of cochlear duct length.

RESULTS

The analyses showed good agreement between manual and automatic measurements of cochlear diameters, with the exception of cochlear height, where a significant difference was observed. Some discrepancies were noted for the prediction of the cochlear length duct without, however, a significant impact. Predictions of insertion angles based on automated measurements were comparable to the postoperative evaluations, with no significant difference from the manual ones.

DISCUSSION

The robustness of automated assessments is essential for integration into clinical practice. Automated measurements of cochlear dimensions are comparable to manual ones. However, image quality and the presence of anatomical abnormalities may influence the results. In this study, the evaluation of the insertion angle prediction was strengthened by comparison with postoperative results taking into account the actual insertion depth.

Use of Hearing Aids Embedded with Inertial Sensors and Artificial Intelligence to Identify Patients at Risk for Falling

OBJECTIVE

To compare fall risk scores of hearing aids embedded with inertial measurement units (IMU-HAs) and powered by artificial intelligence (AI) algorithms with scores by trained observers.

STUDY DESIGN

Prospective, double-blinded, observational study of fall risk scores between trained observers and those of IMU-HAs.

SETTING

Tertiary referral center.

PATIENTS

Two hundred fifty participants aged 55-100 years who were at risk for falls.

INTERVENTIONS

Fall risk was categorized using the Stopping Elderly Accidents, Deaths, and Injuries (STEADI) test battery consisting of the 4-Stage Balance, Timed Up and Go (TUG), and 30-Second Chair Stand tests. Performance was scored using bilateral IMU-HAs and compared to scores by clinicians blinded to the hearing aid measures.

MAIN OUTCOME MEASURES

Fall risk categorizations based on 4-Stage Balance, Timed Up and Go (TUG), and 30-Second Chair Stand tests obtained from IMU-HAs and clinicians.

RESULTS

Interrater reliability was excellent across all clinicians. The 4-Stage Balance and TUG showed no statistically significant differences between clinician and HAs. However, the IMU-HAs failed to record a response in 12% of TUG trials. For the 30-Second Chair Stand test, there was a significant difference of nearly one stand count, which would have altered fall risk classification in 21% of participants.

CONCLUSIONS

These results suggest that fall risk as determined by the STEADI tests was in most instances similar for IMU-HAs and trained observers; however, differences were observed in certain situations, suggesting improvements are needed in the algorithm to maximize accurate fall risk categorization.

Improved radiological imaging of congenital aural atresia using flat-panel volume CT

BACKGROUND

Precise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers a high-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy.

AIM OF THE WORK

Evaluation of the use of fpVCTSECO in combination with an otosurgical planning software for a more accurate diagnosis and treatment of congenital aural atresia.

MATERIAL AND METHODS

Seven patients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering.

RESULTS

Imaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. A significant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D.

DISCUSSION

The introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

Comprehensive literature review on the application of the otological surgical planning software OTOPLAN® for cochlear implantation

BACKGROUND

The size of the human cochlear, measured by the diameter of the basal turn, varies between 7 and 11 mm. For hearing rehabilitation with cochlear implants (CI), the size of the cochlear influences the individual frequency map and the choice of electrode length. OTOPLAN® (CAScination AG [Bern, Switzerland] in cooperation with MED-EL [Innsbruck, Austria]) is a software tool with CE marking for clinical applications in CI treatment which allows for precise pre-planning based on cochlear size. This literature review aims to analyze all published data on the application of OTOPLAN®.

MATERIALS AND METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied to identify relevant studies published in the PubMed search engine between January 2015 and February 2023 using the search terms "otoplan" [title/abstract] OR "anatomy-based fitting" [title/abstract] OR "otological software tool" [title/abstract] OR "computed tomography-based software AND cochlear" [title/abstract].

RESULTS

The systematic review of the literature identified 32 studies on clinical use of OTOPLAN® in CI treatment. Most studies were reported from Germany (7 out of 32), followed by Italy (5), Saudi Arabia (4), the USA (4), and Belgium (3); 2 studies each were from Austria and China, and 1 study from France, India, Norway, South Korea, and Switzerland. In the majority of studies (22), OTOPLAN® was used to assess cochlear size, followed by visualizing the electrode position using postoperative images (5), three-dimensional segmentation of temporal bone structures (4), planning the electrode insertion trajectory (3), creating a patient-specific frequency map (3), planning of a safe drilling path through the facial recess (3), and measuring of temporal bone structures (1).

CONCLUSION

To date, OTOPLAN® is the only DICOM viewer with CE marking in the CI field that can process pre-, intra-, and postoperative images in the abovementioned applications.

[Improved radiological imaging of congenital aural atresia using flat-panel volume CT. German version]

BACKGROUND

Precise preoperative radiological evaluation of aural atresia is of utmost importance for surgical planning. Until now, multislice computed tomography (MSCT) has been used but it cannot adequately visualize small structures such as the stapes. Flat-panel volume CT (fpVCT) with its secondary reconstructions (fpVCTSECO) offers a high-resolution visualization of the middle ear. New otosurgical planning software also enables detailed 3D reconstruction of the middle ear anatomy.

AIM OF THE WORK

Evaluation of the use of fpVCTSECO in combination with an otosurgical planning software for a more accurate diagnosis and treatment of congenital aural atresia.

MATERIAL AND METHODS

Seven patients with congenital aural atresia underwent preoperative MSCT (600 µm slice thickness) and corresponding fpVCT (466 µm slice thickness). In addition, fpVCTSECO (99 µm slice thickness) were reconstructed. The Jahrsdoerfer and Siegert grading scores were determined and their applicability in the abovementioned imaging modalities was evaluated. In addition, the malleus incus complex was analyzed in 3D rendering.

RESULTS

Imaging with fpVCTSECO enabled reliable visualization of the abnormalities, in particular the ossicular chain. A significant difference in the Siegert grading score was found. In addition, the malleus-incus complex could be visualized better in 3D.

DISCUSSION

The introduction of new imaging techniques and surgical planning techniques into the diagnostic concept of aural atresia facilitates the identification of malformed anatomy and enables systematic analysis. This combination can also help to more accurately classify the pathology and thus increase the safety and success of the surgical procedure.

Tonotopic and Default Frequency Fitting for Music Perception in Cochlear Implant Recipients: A Randomized Clinical Trial

Importance

Cochlear implants are an effective technique for enhancing speech perception abilities in quiet environments for people with severe to profound deafness. Nevertheless, complex sound signals perception, such as music perception, remains challenging for cochlear implant users.

Objective

To assess the benefit of a tonotopic map on music perception in new cochlear implant users.

Design, Setting, and Participants

A prospective, randomized, double-blind, 2-period crossover study including 26 new cochlear implant users was performed over a 6-month period (June 2021 to November 2021). An anatomical tonotopic map was created using postoperative flat-panel computed tomography and a reconstruction software based on Greenwood function. New cochlear implant users older than 18 years with bilateral severe to profound sensorineural hearing loss or complete hearing loss for less than 5 years were selected in the University Hospital Centre of Rennes in France. The trial was conducted from June to November 2021 (inclusion) and to February 2022 (end of the assessment procedure at 12 weeks postactivation), and the analysis itself was completed in December 2022.

Intervention

Each participant was randomized to receive a conventional map followed by a tonotopic map or vice versa.

Main Outcomes and Measures

Participants performed pitch-scaling tasks (multidimensional qualitative assessment, melodic contour identification, melodic recognition test) after 6 weeks of each setting.

Results

Thirteen participants were randomized to each sequence. Two of the 26 participants recruited (1 in each sequence) had to be excluded due to the COVID-19 pandemic. The multidimensional qualitative assessment (Gabrielsson test), melodic contour identification, and melodic recognition scores were significantly higher with the tonotopic setting than the conventional one (mean effect [ME], 7.8; 95% CI, 5.0-10.5; ME, 12.1%; 95% CI, 5.7%-18.4%; ME, 14.4%, 95% CI, 8.5%-20.2%; and ME, 2.1, 95% CI, 1.7-2.5, respectively). Among the different dimensions evaluated by the Gabrielsson test, the mean scores for clarity, spaciousness, fullness, nearness, and total impression were significantly higher with tonotopic fitting. Ninety-two percent of the participants kept the tonotopy-based map after the study period.

Conclusions

In this randomized clinical trial of patients with new cochlear implants, a tonotopic-based fitting was associated with better results in perception of complex sound signals such as music listening experience.

Trial Registration

ClinicalTrials.gov Identifier: NCT04922619.

[Comprehensive literature review on the application of the otological-surgical planning software OTOPLAN® for cochlear implantation. German version]

BACKGROUND

The size of the human cochlear, measured by the diameter of the basal turn, varies between 7 and 11 mm. For hearing rehabilitation with cochlear implants (CI), the size of the cochlear influences the individual frequency map and the choice of electrode length. OTOPLAN® (CAScination AG [Bern, Switzerland] in cooperation with MED-EL [Innsbruck, Austria]) is a software tool with CE marking for clinical applications in CI treatment which allows for precise pre-planning based on cochlear size. This literature review aims to analyze all published data on the application of OTOPLAN®.

MATERIALS AND METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied to identify relevant studies published in the PubMed search engine between January 2015 and February 2023 using the search terms "otoplan" [title/abstract] OR "anatomy-based fitting" [title/abstract] OR "otological software tool" [title/abstract] OR "computed tomography-based software AND cochlear" [title/abstract].

RESULTS

The systematic review of the literature identified 32 studies on clinical use of OTOPLAN® in CI treatment. Most studies were reported from Germany (7 out of 32), followed by Italy (5), Saudi Arabia (4), the USA (4), and Belgium (3); 2 studies each were from Austria and China, and 1 study from France, India, Norway, South Korea, and Switzerland. In the majority of studies (22), OTOPLAN® was used to assess cochlear size, followed by visualizing the electrode position using postoperative images (5), three-dimensional segmentation of temporal bone structures (4), planning the electrode insertion trajectory (3), creating a patient-specific frequency map (3), planning of a safe drilling path through the facial recess (3), and measuring of temporal bone structures (1).

CONCLUSION

To date, OTOPLAN® is the only DICOM viewer with CE marking in the CI field that can process pre-, intra-, and postoperative images in the abovementioned applications.

The Photon-Counting CT Enters the Field of Cochlear Implantation: Comparison to Angiography DynaCT and Conventional Multislice CT

INTRODUCTION

Cochlear duct length (CDL) measurement plays a role in the context of individualized cochlear implant (CI) surgery regarding an individualized selection and implantation of the CI electrode carrier and an efficient postoperative anatomy-based fitting process. The level of detail of the preoperative temporal bone CT scan depends on the imaging modality with major impact on CDL measurements and CI electrode contact position determination. The aim of this study was to evaluate the accuracy of perioperative CDL measurements and electrode contact determination in photon-counting CT (PCCT).

METHODS

Ten human fresh-frozen petrous bone specimens were examined with a first-generation PCCT. A clinically applicable radiation dose of 27.1 mGy was used. Scans were acquired before and after CI insertion. Postoperative measurement of the CDL was conducted using an otological planning software and 3D-curved multiplanar reconstruction. Investigation of electrode contact position was performed by two respective observers. Measurements were compared with a conventional multislice CT and to a high-resolution flat-panel volume CT with secondary reconstructions.

RESULTS

Pre- and postoperative CDL measurements in PCCT images showed no significant difference to high-resolution flat-panel volume CT. Postoperative CI electrode contact determination was also as precise as the flat-panel CT-based assessment. PCCT and flat-panel volume CT were equivalent concerning interobserver variability.

CONCLUSION

CDL measurement with PCCT was equivalent to flat-panel volume CT with secondary reconstructions. PCCT enabled highly precise postoperative CI electrode contact determination with substantial advantages over conventional multislice CT scanners.

Dependence of Cochlear Duct Length Measurement on the Resolution of the Imaging Dataset

HYPOTHESIS

Measurements of the cochlear duct length (CDL) are dependent on the resolution of the imaging dataset.

BACKGROUND

Previous research has shown highly precise cochlear measurements using 3D-curved multiplanar reconstruction (MPR) and flat-panel volume computed tomography (fpVCT). Thus far, however, there has been no systematic evaluation of the imaging dataset resolution required for optimal CDL measurement. Therefore, the aim of this study was to evaluate the dependence of CDL measurement on the resolution of the imaging dataset to establish a benchmark for future CDL measurements.

METHODS

fpVCT scans of 10 human petrous bone specimens were performed. CDL was measured using 3D-curved MPR with secondary reconstruction of the fpVCT scans (fpVCT SECO ) and increasing resolution from 466 to 99 μm. In addition, intraobserver variability was evaluated. A best-fit function for calculation of the CDL was developed to provide a valid tool when there are no measurements done with high-resolution imaging datasets.

RESULTS

Comparison of different imaging resolution settings showed significant differences for CDL measurement in most of the tested groups ( p < 0.05), except for the two groups with the highest resolution. Imaging datasets with a resolution lower than 200 μm showed lower intraobserver variability than the other resolution settings, although there were no clinically unacceptable errors with respect to the Bland-Altman plots. The developed best-fit function showed high accuracy for CDL calculation using resolution imaging datasets of 300 μm or lower.

CONCLUSION

3D-curved MPR in fpVCT with a resolution of the imaging dataset of 200 μm or higher revealed the most precise CDL measurement. There was no benefit of using a resolution higher than 200 μm with regard to the accuracy of the CDL measurement.

Comparison of Tonotopic and Default Frequency Fitting for Speech Understanding in Noise in New Cochlear Implantees: A Prospective, Randomized, Double-Blind, Cross-Over Study

OBJECTIVES

While cochlear implants (CIs) have provided benefits for speech recognition in quiet for subjects with severe-to-profound hearing loss, speech recognition in noise remains challenging. A body of evidence suggests that reducing frequency-to-place mismatch may positively affect speech perception. Thus, a fitting method based on a tonotopic map may improve speech perception results in quiet and noise. The aim of our study was to assess the impact of a tonotopic map on speech perception in noise and quiet in new CI users.

DESIGN

A prospective, randomized, double-blind, two-period cross-over study in 26 new CI users was performed over a 6-month period. New CI users older than 18 years with bilateral severe-to-profound sensorineural hearing loss or complete hearing loss for less than 5 years were selected in the University Hospital Centre of Rennes in France. An anatomical tonotopic map was created using postoperative flat-panel computed tomography and a reconstruction software based on the Greenwood function. Each participant was randomized to receive a conventional map followed by a tonotopic map or vice versa. Each setting was maintained for 6 weeks, at the end of which participants performed speech perception tasks. The primary outcome measure was speech recognition in noise. Participants were allocated to sequences by block randomization of size two with a ratio 1:1 (CONSORT Guidelines). Participants and those assessing the outcomes were blinded to the intervention.

RESULTS

Thirteen participants were randomized to each sequence. Two of the 26 participants recruited (one in each sequence) had to be excluded due to the COVID-19 pandemic. Twenty-four participants were analyzed. Speech recognition in noise was significantly better with the tonotopic fitting at all signal-to-noise ratio (SNR) levels tested [SNR = +9 dB, p = 0.002, mean effect (ME) = 12.1%, 95% confidence interval (95% CI) = 4.9 to 19.2, standardized effect size (SES) = 0.71; SNR = +6 dB, p < 0.001, ME = 16.3%, 95% CI = 9.8 to 22.7, SES = 1.07; SNR = +3 dB, p < 0.001 ME = 13.8%, 95% CI = 6.9 to 20.6, SES = 0.84; SNR = 0 dB, p = 0.003, ME = 10.8%, 95% CI = 4.1 to 17.6, SES = 0.68]. Neither period nor interaction effects were observed for any signal level. Speech recognition in quiet ( p = 0.66) and tonal audiometry ( p = 0.203) did not significantly differ between the two settings. 92% of the participants kept the tonotopy-based map after the study period. No correlation was found between speech-in-noise perception and age, duration of hearing deprivation, angular insertion depth, or position or width of the frequency filters allocated to the electrodes.

CONCLUSION

For new CI users, tonotopic fitting appears to be more efficient than the default frequency fitting because it allows for better speech recognition in noise without compromising understanding in quiet.

Otological Planning Software-OTOPLAN: A Narrative Literature Review

The cochlear implant (CI) is a widely accepted option in patients with severe to profound hearing loss receiving limited benefit from traditional hearing aids. CI surgery uses a default setting for frequency allocation aiming to reproduce tonotopicity, thus mimicking the normal cochlea. One emerging instrument that may substantially help the surgeon before, during, and after the surgery is a surgical planning software product developed in collaboration by CASCINATION AG (Bern, Switzerland) and MED-EL (Innsbruck Austria). The aim of this narrative review is to present an overview of the main features of this otological planning software, called OTOPLAN®. The literature was searched on the PubMed and Web of Science databases. The search terms used were "OTOPLAN", "cochlear planning software" "three-dimensional imaging", "3D segmentation", and "cochlear implant" combined into different queries. This strategy yielded 52 publications, and a total of 31 studies were included. The review of the literature revealed that OTOPLAN is a useful tool for otologists and audiologists as it improves preoperative surgical planning both in adults and in children, guides the intraoperative procedure and allows postoperative evaluation of the CI.

Accuracy of Preoperative Cochlear Duct Length Estimation and Angular Insertion Depth Prediction

OBJECTIVE

In cochlear implantation with flexible lateral wall electrodes, a cochlear coverage of 70% to 80% is assumed to yield an optimal speech perception. Therefore, fitting the cochlear implant (CI) to the patient's individual anatomy has gained importance in recent years. For these reasons, the optimal angular insertion depth (AID) has to be calculated before cochlear implantation. One CI manufacturer offers a software that allows to visualize the AID of different electrode arrays. Here, it is hypothesized that these preoperative AID models overestimate the postoperatively measured insertion angle. This study aims to investigate the agreement between preoperatively estimated and postoperatively measured AID.

STUDY DESIGN

Retrospective cross-sectional study.

SETTING

Single-center tertiary referral center.

PATIENTS

Patients undergoing cochlear implantation.

INTERVENTION

Preoperative and postoperative high-resolution computed tomography (HRCT).

MAIN OUTCOME MEASURES

The cochlear duct length was estimated by determining cochlear parameters ( A value and B value), and the AID for the chosen electrode was (i) estimated by elliptic circular approximation by the software and (ii) measured manually postoperatively by detecting the electrode contacts after insertion.

RESULTS

A total of 80 HRCT imaging data sets from 69 patients were analyzed. The mean preoperative AID estimation was 662.0° (standard deviation [SD], 61.5°), and the mean postoperatively measured AID was 583.9° (SD, 73.6°). In all cases (100%), preoperative AID estimation significantly overestimated the postoperative determined insertion angle (mean difference, 38.1°). A correcting factor of 5% on preoperative AID estimation dissolves these differences.

CONCLUSIONS

The use of an electrode visualization tool may lead to shorter electrode array choices because of an overestimation of the insertion angle. Applying a correction factor of 0.95 on preoperative AID estimation is recommended.

Validation of Automatic Cochlear Measurements Using OTOPLAN® Software

INTRODUCTION

Electrode length selection based on case-related cochlear parameters is becoming a standard pre-operative step for cochlear implantation. The manual measurement of the parameters is often time-consuming and may lead to inconsistencies. Our work aimed to evaluate a novel, automatic measurement method.

MATERIALS AND METHODS

A retrospective evaluation of pre-operative HRCT images of 109 ears (56 patients) was conducted, using a development version of the OTOPLAN^® software. Inter-rater (intraclass) reliability and execution time were assessed for manual (surgeons R1 and R2) vs. automatic (AUTO) results. The analysis included A-Value (Diameter), B-Value (Width), H-Value (Height), and CDLOC-length (Cochlear Duct Length at Organ of Corti/Basilar membrane).

RESULTS

The measurement time was reduced from approximately 7 min ± 2 (min) (manual) to 1 min (AUTO). Cochlear parameters in mm (mean ± SD) for R1, R2 and AUTO, respectively, were A-value: 9.00 ± 0.40, 8.98 ± 0.40 and 9.16 ± 0.36; B-value: 6.81 ± 0.34, 6.71 ± 0.35 and 6.70 ± 0.40; H-value: 3.98 ± 0.25, 3.85 ± 0.25 and 3.76 ± 0.22; and the mean CDLoc-length: 35.64 ± 1.70, 35.20 ± 1.71 and 35.47 ± 1.87. AUTO CDLOC measurements were not significantly different compared to R1 and R2 (H0: Rx CDLOC = AUTO CDLOC: p = 0.831, p = 0.242, respectively), and the calculated intraclass correlation coefficient (ICC) for CDLOC was 0.9 (95% CI: 0.85, 0.932) for R1 vs. AUTO; 0.90 (95% CI: 0.85, 0.932) for R2 vs. AUTO; and 0.893 (95% CI: 0.809, 0.935) for R1 vs. R2.

CONCLUSIONS

We observed excellent inter-rater reliability, a high agreement of outcomes, and reduced execution time using the AUTO method.

Accuracy of radiological prediction of electrode position with otological planning software and implications of high-resolution imaging

OBJECTIVES

In cochlear implantation, preoperative prediction of electrode position has recently gained increasing attention. Currently, planning is usually done by multislice CT (MSCT). However, flat-panel volume CT (fpVCT) and its secondary reconstructions (fpVCTSECO) allow for more precise visualization of the cochlea. Combined with a newly developed otological planning software, the position of every single contact can be effectively predicted. In this study it was investigated how accurately radiological prediction forecasts the postoperative electrode localization and whether higher image resolution is advantageous.

METHODS

Utilizing otological planning software (OTOPLAN®) and different clinical imaging modalities (MSCT, fpVCT and fpVCTSECO) the electrode localization [angular insertion depth (AID)] and respective contact frequencies were predicted preoperatively and examined postoperatively. Furthermore, inter-electrode-distance (IED) and inter-electrode-frequency difference (IEFD) were evaluated postoperatively.

RESULTS

Measurements revealed a preoperative overestimation of AID. Corresponding frequencies were also miscalculated. Determination of IED and IEFD revealed discrepancies at the transition from the basal to the middle turn and round window to the basal turn. All predictions and discrepancies were lowest when using fpVCTSECO.

CONCLUSION

The postoperative electrode position can be predicted quite accurately using otological planning software. However, because of several potential misjudgments, high-resolution imaging, such as offered by fpVCTSECO, should be used pre- and postoperatively.

Intra- and Interrater Reliability of CT- versus MRI-Based Cochlear Duct Length Measurement in Pediatric Cochlear Implant Candidates and Its Impact on Personalized Electrode Array Selection

Background: Radiological high-resolution computed tomography-based evaluation of cochlear implant candidates’ cochlear duct length (CDL) has become the method of choice for electrode array selection. The aim of the present study was to evaluate if MRI-based data match CT-based data and if this impacts on electrode array choice. Methods: Participants were 39 children. CDL, length at two turns, diameters, and height of the cochlea were determined via CT and MRI by three raters using tablet-based otosurgical planning software. Personalized electrode array length, angular insertion depth (AID), intra- and interrater differences, and reliability were calculated. Results: Mean intrarater difference of CT- versus MRI-based CDL was 0.528 ± 0.483 mm without significant differences. Individual length at two turns differed between 28.0 mm and 36.6 mm. Intrarater reliability between CT versus MRI measurements was high (intra-class correlation coefficient (ICC): 0.929–0.938). Selection of the optimal electrode array based on CT and MRI matched in 90.1% of cases. Mean AID was 629.5° based on the CT and 634.6° based on the MRI; this is not a significant difference. ICC of the mean interrater reliability was 0.887 for the CT-based evaluation and 0.82 for the MRI-based evaluation. Conclusion: MRI-based CDL measurement shows a low intrarater difference and a high interrater reliability and is therefore suitable for personalized electrode array selection.

[Measuring the cochlea using a tablet-based software package: influence of imaging modality and rater background]

BACKGROUND

Cochlear duct length (CDL) is subject to significant individual variation. In the context of cochlear implantation, adapting the electrode array length to the CDL is of potential interest, as it has been associated with improvements in both speech recognition and sound quality. Using a tablet-based software package, it is possible to measure CDL at the level of the organ of Corti (CDLOC) to select appropriate electrode array lengths based on individual cochlear anatomy.

OBJECTIVE

To identify effects of imaging modality and rater background on CDL estimates.

METHODS

Magnetic resonance imaging (MRI) and flat-panel volume CT (fpVCT) scans of 10 patients (20 cochleae) were analyzed using the OTOPLAN software package (MED-EL, Innsbruck, Austria). Raters were an otorhinolaryngology (ORL) specialist, an ORL resident, and an audiologist. To analyze effects of rater background and imaging modality on CDL measurements, linear mixed models were constructed.

RESULTS

Measurements showed mean CDLOC(fpVCT) = 36.69 ± 1.78 mm and CDLOC(MRI) = 36.81 ± 1.87 mm. Analyses indicated no significant effect of rater background (F(2, 105) = 0.84; p = 0.437) on CDL estimates. Imaging modality, on the other hand, significantly affected CDL (F (1, 105) = 20.70; p < 0.001), whereby estimates obtained using MRI were 0.89 mm larger than those obtained using fpVCT.

CONCLUSION

No effect of rater background on CDL estimates could be identified, suggesting that comparable measurements could be obtained by personnel other than specially trained neurootologists. While imaging modality (fpVCT vs. MRI) did impact CDL results, the difference was small and of questionable clinical significance.

Anatomical Variations of the Epitympanum and the Usable Space for Middle Ear Implants Analyzed With CT-assisted Imaging Using a Tablet-based Software

OBJECTIVE

To evaluate interindividual anatomical variations of the epitympanum and the usable space for implantation of active middle ear implants (AMEI) as well as the usefulness of a tablet-based software to assess individual anatomy on computed tomography (CT) scans.

PATIENTS

CT scans of 126 patients, scheduled for cochlea implantation (50.8% men; 0.6-90.0 yr) without middle ear malformations or previous middle ear surgery and with slice thickness ≤0.7 mm were analyzed.

MAIN OUTCOME MEASURES

Since no standardized measurements to assess the size of the epitympanum are available, relevant distances were defined according to anatomical landmarks. Three independent raters measured these distances using a tablet-based software. Interrater correlation was computed to evaluate the quality of the measurement process. Descriptive data were analyzed for validation and for evaluation of interindividual anatomical variations. Influence of age and sex on the taken measurements was assessed.

RESULTS

No relevant correlation between age or sex and the anatomy of the epitympanum was found. Interrater correlation ranged from Spearman's ρ = 0.3-0.9 and there were significant differences between individual rater results for various combinations. Descriptive data revealed high interindividual anatomical variance of the epitympanum, especially regarding the distance between incus and skull base.

CONCLUSION

The reported descriptive data regarding the anatomy of the epitympanum emphasizes the importance of preoperative planning, especially since the height of the epitympanum showed great interindividual variance potentially limiting implantation of AMEIs. The herein used tablet-based software seems to be convenient for preoperative assessment of individual anatomy in the hand of otosurgeons.

Robotic Cochlear Implant Surgery: Imaging-Based Evaluation of Feasibility in Clinical Routine

Background: Robotic surgery has been proposed in various surgical fields to reduce recovery time, scarring, and to improve patients' outcomes. Such innovations are ever-growing and have now reached the field of cochlear implantation. To implement robotic ear surgery in routine, it is of interest if preoperative planning of a safe trajectory to the middle ear is possible with clinically available image data.

Methods: We evaluated the feasibility of robotic cochlear implant surgery in 50 patients (100 ears) scheduled for routine cochlear implant procedures based on clinically available imaging. The primary objective was to assess if available high-resolution computed tomography or cone beam tomography imaging is sufficient for planning a trajectory by an otological software. Secondary objectives were to assess the feasibility of cochlear implant surgery with a drill bit diameter of 1.8 mm, which is the currently used as a standard drill bit. Furthermore, it was evaluated if feasibility of robotic surgery could be increased when using smaller drill bit sizes. Cochlear and trajectory parameters of successfully planned ears were collected. Measurements were carried out by two observers and the interrater reliability was assessed using Cohen's Kappa.

Results: Under the prerequisite of the available image data being sufficient for the planning of the procedure, up to two thirds of ears were eligible for robotic cochlear implant surgery with the standard drill bit size of 1.8 mm. The main reason for inability to plan the keyhole access was insufficient image resolution causing anatomical landmarks not being accurately identified. Although currently not applicable in robotic cochlear implantation, narrower drill bit sizes ranging from 1.0 to 1.7 mm in diameter could increase feasibility up to 100%. The interrater agreement between the two observers was good for this data set.

Discussion: For robotic cochlear implant surgery, imaging with sufficient resolution is essential for preoperative assessment. A slice thickness of <0.3 mm is necessary for trajectory planning. This can be achieved by using digital volume tomography while radiation exposure can be kept to a minimum. Furthermore, surgeons who use the software tool, should be trained on a regular basis in order to achieve planning consistency.

Cochlear Duct Length Measurements in Computed Tomography and Magnetic Resonance Imaging Using Newly Developed Techniques

Objective

Growing interest in measuring the cochlear duct length (CDL) has emerged, since it can influence the selection of cochlear implant electrodes. Currently the measurements are performed with ionized radiation imaging. Only a few studies have explored CDL measurements in magnetic resonance imaging (MRI). Therefore, the presented study aims to fill this gap by estimating CDL in MRI and comparing it with multislice computed tomography (CT).

Study Design

Retrospective data analyses of 42 cochleae.

Setting

Tertiary care medical center.

Methods

Diameter (A value) and width (B value) of the cochlea were measured in HOROS software. The CDL and the 2-turn length were determined by the elliptic circular approximation (ECA). In addition, the CDL, the 2-turn length, and the angular length were determined via HOROS software by the multiplanar reconstruction (MPR) method.

Results

CDL values were significantly shorter in MRI by MPR (d = 1.38 mm, P < .001) but not by ECA. Similar 2-turn length measurements were significantly lower in MRI by MPR (d = 1.67 mm) and ECA (d = 1.19 mm, both P < .001). In contrast, angular length was significantly higher in MRI (d = 26.79°, P < .001). When the values were set in relation to the frequencies of the cochlea, no clinically relevant differences were estimated (58 Hz at 28-mm CDL).

Conclusion

In the presented study, CDL was investigated in CT and MRI by using different approaches. Since no clinically relevant differences were found, diagnostics with radiation may be omitted prior to cochlear implantation; thus, a concept of radiation-free cochlear implantation could be established.

Influence of electrode to cochlear duct length ratio on post-operative speech understanding outcomes

OBJECTIVE

To assess whether the pre-operative electrode to cochlear duct length ratio (ECDLR), is associated with post-operative speech recognition outcomes.

STUDY DESIGN

A retrospective chart review study.

SETTING

Tertiary referral center.

PATIENTS

The study included sixty-one adult CI recipients with a pre-operative computed tomography scan and a speech recognition test 12 months after implantation.

INTERVENTIONS

The average of two raters' cochlear duct length (CDL) measurements and the length of the recipient's cochlear implant electrode array formed the basis for the electrode-to-cochlear duct length ratio (ECLDR). Speech recognition tests were compared as a function of ECDLR and electrode array length itself.

MAIN OUTCOME MEASURES

The relationship between ECDLR and percent correct on speech recognition tests.

RESULTS

A second order polynomial regression relating ECDLR to percent correct on the CNC words speech recognition test was statistically significant, as was a fourth order polynomial regression for the AzBio Quiet test. In contrast, there was no statistically significant relationship between speech recognition scores and electrode array length.

CONCLUSIONS

ECDLR values can be statistically associated to speech-recognition outcomes. However, these ECDLR values cannot be predicted by the electrode length alone, and must include a measure of CDL.

Fully Automated Measurement of Cochlear Duct Length From Clinical Temporal Bone Computed Tomography

OBJECTIVES/HYPOTHESIS

To present and validate a novel fully automated method to measure cochlear dimensions, including cochlear duct length (CDL).

STUDY DESIGN

Cross-sectional study.

METHODS

The computational method combined 1) a deep learning (DL) algorithm to segment the cochlea and otic capsule and 2) geometric analysis to measure anti-modiolar distances from the round window to the apex. The algorithm was trained using 165 manually segmented clinical computed tomography (CT). A Testing group of 159 CTs were then measured for cochlear diameter and width (A- and B-values) and CDL using the automated system and compared against manual measurements. The results were also compared with existing approaches and historical data. In addition, pre- and post-implantation scans from 27 cochlear implant recipients were studied to compare predicted versus actual array insertion depth.

RESULTS

Measurements were successfully obtained in 98.1% of scans. The mean CDL to 900° was 35.52 mm (SD, 2.06; range, [30.91-40.50]), the mean A-value was 8.88 mm (0.47; [7.67-10.49]), and mean B-value was 6.38 mm (0.42; [5.16-7.38]). The R² fit of the automated to manual measurements was 0.87 for A-value, 0.70 for B-value, and 0.71 for CDL. For anti-modiolar arrays, the distance between the imaged and predicted array tip location was 0.57 mm (1.25; [0.13-5.28]).

CONCLUSION

Our method provides a fully automated means of cochlear analysis from clinical CTs. The distribution of CDL, dimensions, and cochlear quadrant lengths is similar to those from historical data. This approach requires no radiographic experience and is free from user-related variation.

LEVEL OF EVIDENCE

3 Laryngoscope, 2021.

Implementation of secondary reconstructions of flat-panel volume computed tomography (fpVCT) and otological planning software for anatomically based cochlear implantation

Purpose

For further improvements in cochlear implantation, the measurement of the cochlear duct length (CDL) and the determination of the electrode contact position (ECP) are increasingly in the focus of clinical research. Usually, these items were investigated by multislice computed tomography (MSCT). The determination of ECP was only possible by research programs so far. Flat-panel volume computed tomography (fpVCT) and its secondary reconstructions (fpVCT_SECO) allow for high spatial resolution for the visualization of the temporal bone structures. Using a newly developed surgical planning software that enables the evaluation of CDL and the determination of postoperative ECP, this study aimed to investigate the combination of fpVCT and otological planning software to improve the implementation of an anatomically based cochlear implantation.

Methods

Cochlear measurements were performed utilizing surgical planning software in imaging data (MSCT, fpVCT and fpVCT_SECO) of patients with and without implanted electrodes.

Results

Measurement of the CDL by the use of an otological planning software was highly reliable using fpVCT_SECO with a lower variance between the respective measurements compared to MSCT. The determination of the inter-electrode-distance (IED) between the ECP was improved in fpVCT_SECO compared to MSCT.

Conclusion

The combination of fpVCT_SECO and otological planning software permits a simplified and more reliable analysis of the cochlea in the pre- and postoperative setting. The combination of both systems will enable further progress in the development of an anatomically based cochlear implantation.